Adjustable sheave



Dec. 28, 1954 FlRTH 2,697,947

ADJUSTABLE SHE-AVE Filed March 20, 1952 6 Sheds-Sheet 1 Dec. 28, 1954 D, F 2,697,94?

ADJUSTABLE SHEAVE Filed March 20, .1952 6 Sheets-Sheet 2 Dec. 28, 1954 D. FIRTH 2,697,947

ADJUSTABLE SHEAVE Filed March 20, 1952 6 Sheets-Sheet 3 INVENTUR. .DQZ/Zdfirfiq BY Dec. 28, 1954 D, PE

ADJUSTABLE SHEAVE Filed march 20, 1952 6 Sheets-Sheet 4 Dec. 28, 1954 D. FIRTH ADJUSTABLE SHEAVE 6 Sheets-Sheet 5 Filed March 20, 1952 INVENTOR. .flQZ/Ld Eff/W Dec. 28,- 1954 Filed March 20, 1952 D. FIRTH ADJUSTABLE SHEAVB 6 Sheets-Sheet 6 INVENTOR.

United States PatentO ADJUSTABLE SHEAVE David Firth, South Bend, Ind., assignor to Dodge Manufacturing Corporation, Mishawaka, Ind., a corporation of Indiana Application March 20, 1952, Serial No. 277,638

21 Claims. (Cl. 74-23017) This invention relates to variable pitch V-belt sheaves, and more especially to sheaves of the type comprising two interarranged and oppositely axially shiftable groups of annular discs cooperating to form belt grooves, the disc's of each group being rigidly connected in spaced relation and arranged in alternation with and confronting the discs of the other group. An example of a sheave of this typeis disclosed in the patent to Firth et al., No. 2,400,294 of May 14, 1946.

The present invention has to do with the matter of adjusting the relative positions of the two groups of connected discs' for varying the effective diameter of the sheave, and further with the matters of mounting the sheave on a shaft and locking the sheave discs in adjusted position on the sheave hub.

With respect to the adjusting means, the invention embraces different species, each comprising a differential adjusting screw arranged beside and parallel with the sheave hub in the surrounding adjustable sheave body, said screw having a coarse threaded portion in threaded engagement with one of the sheave discs and a fine threaded portion engaged by a non-rotatable nut in fixed position on the hub. The coarse and fine threads of the screw progress in the same direction, the screw being either right handed or left handed with respect to both threads. Due to the difference in pitch of said threads, the screw when turned will move the disc in which it is threaded in a direction opposite to that which the screw moves axially. As said disc is one of a connected group, the whole group will move in said direction. The screw is connected to the other group of discs for moving the latter axially with the screw. Hence a turn of the screw will cause said groups to move simultaneously in opposite directions. Preferably the pitch of the coarse thread of the screw is twice that of the fine thread. Hence by turning the screw the two groups of discs are moved equal distances in opposite directions, thereby changmg the effective diameter of the sheave without shifting the centers of the belt grooves relative to the sheave hub. The total relative movement of said groups of discs is twice that which the screw moves axially, thereby obtaining a relatively large range of adjustment for a comparatively short travel of the adjusting screw.

Thus the adjusting means gives the same desirable results that are obtained by the adjusting means disclosed in said patent to Firth et a1. Besides giving these results, the adjusting means of the present invention is advantageous for simplicity, compactness, minimization of overall length of the sheave, and economical manufacture on a mass production basis. It requires little or no extra space for its accommodation, avoids protrusion of adjusting means from or beyond either end of the sheave body, and at the same time avoids such complications as are incident to, use of an adjusting screw within the hub. Said adjusting means is also of particular advantage in connection with and to permit utilization of other principal features of the invention.

Said other principal features include the mounting of the sheave discs on a longitudinally split hub expansible to grip the discs in the bores thereof, for locking them in a most advantageous manner in adjusted position, and the provision of means for fastening the sheave on a shaft by the agency of a tapered bushing wedgeable and dewedgeable by means within the hub.

The invention has in view, among other objects, the provision of ,a sheave practicable for use under condi- 2,697,947 Patented Dec. 28, 1954 tions requiring very exact adjusting, as for example in V-belt drives for spinning frames of certain machines used in the textile industry, which spinning frames, on account of the size and texture of the yarn to be spun, must be driven at precise speeds. It is found that sheave discs loose on the hub, though splined thereto, tend to wear grooves in the hub, which may interfere with or render it exceedingly difiicult to do precision adjusting. If the discs after wearing grooves in the hub are adjusted to positions only minutely offset from said grooves, they are likely to get back into the grooves while the sheave is in operative use, resulting in imperfect adjustment. Moreover the slight relative radial movements between loose discs and the hub which take place in every revolution of the sheave tends to cause corrosion of contacting surfaces. It is therefore highly desirable, especially in sheaves for use under such exacting conditions as above indicated, to lock the discs fast to the hub by expanding the latter in said discs. Such locking is also desirable to prevent rattling.

A sheave of one practicable construction embodying the features of the invention is shown for illustration in Figs. 1 to 11 of the accompanying drawings, the remaining figures of which illustrate modifications with respect to the adjusting means, while Figs. 19 to 22 illustrate a sheave employing an unsplit inexpansible hub.

Fig. 1 is a longitudinal section of an illustrative sheave taken on the staggered line 11 of Fig. 3, showing the sheave in fully contracted state for driving at maximum effective diameter, the V-belts being held by confronting discs in their outermost position in the sheave.

Fig. 2 is a longitudinal half section showing the sheave fully expanded for driving at minimum effective diameter, the V-belts being in the innermost position which they can assume in the sheave.

Fig. 3 is an enlarged front end elevation of the central portion of the sheave, the belt-engaging portions of the sheave discs being broken away.

Figs. 4 and 5 illustrate steps in assembling the adjustable sheave body on the sheave hub.

Fig. 6 is a rear end elevation of the central portion of the sheave.

Fig. 7 is a cross section taken on the staggered line 7-7 of Fig. 1, looking in the direction of the arrows.

Fig. 8 is a longitudinal half section taken on the line 88 of Fig. 3, showing one of the tie bolts and associated spacers by which the discs of one axially shiftable group are connected.

Fig. 9 is a longitudinal half section taken on the staggered line 9-9 of Fig. 3, showing one of the tie bolts and associated spacers by which the discs of the other group are connected.

Fig. 10 is a longitudinal section of the sheave hub.

11 is a front end view of said hub.

Figs. 12 and 13 are longitudinal half sections of dual belt sheaves embodying the invention with respect to the adjusting means in modified forms.

Figs. 14 and 15 illustrate steps in assembling the sheave of Fig. 13.

Fig. 16 is a longitudinal section of a dual belt sheave showing another modification of the adjusting means.

Flgs. 17 and 18 illustrate steps in assembling the sheave of Fig. 16.

Figs. 19 to 22 illustrate a sheave employing a solid or unsplit and inexpansible hub. Fig. 19 is a longitudinal section of the central portion of the sheave, taken on the line 19-19 of Fig. 21. Fig. 20 is a longitudinal section taken on the line 2020 of Fig. 21. Fig. 21 is a front end elevation of Fig. 19. Fig. 22 shows a detail of the sheave.

Figs. 23 and 24 represent solid hub sheaves of a construction generally the same as that of Figs. 19 to 22 but modified as to the specific means for locking the sheave discs in adjusted position.

Referring to Figs. 1 to 11, the illustrative sheave comprises a series of annular discs or sheave sections designated in successive order by the reference numerals 1 to 6 inclusive, the numeral 1 being applied to the front end disc of the series. These are conically faced discs arranged with alternate discs confronting the others and cooperating therewith to form grooves for a plurality of V-belts 7. Thus the series comprises a group or plurality of discs 1, 3 and 5 for engaging corresponding sides of the belts, and a group or plurality of opposing discs '2, 4 and 6 for engaging the other sides of the belts. The two groups of discs are relatively shiftable as units, the discs of each group being rigidly connected in appropriate spaced relation to allow shifting said units simultaneously in opposite directions between the positions shown in Figs. 1 and 2. Any suitable means may be employed for spacing and connecting the discs. In the illustrative sheave, the body construction of which is similar to that of the previously mentioned patent, the discs of each of the two groups aforesaid are uniformly spaced by tubular spacers slidable in the intervening discs of the other group, the discs 1, 3 and 5 and interposed spacers 8 being connected by tie bolts or screws 9 screwed into the disc 5 and having heads countersunk in the foremost disc 1 (Fig. 9), and the discs 2, 4 and 6 and interposed spacers it) being connected .by tie bolts or screws 11 screwed into the disc 2 and having heads countersunk in the rearmost disc 6 (Fig. 8).

A central support for the sheave discs is provided in this instance by a longitudinally split expansible hub 12 adapted to be mounted on a shaft through the medium of a tapered split contractible bushing 13 fitting a tapered portion of the hub bore. The discs fit slidably on the hub in its unexpanded state. Driving connection between the discs and hub is provided by a key 14 fitted in a longitudinal hub groove and slidably fitted in grooves therefor in the discs. The bushing 13 is bored to fit on a stub shaft (not shown)' By operation of means hereinafter described, the bushing can be wedged between the hub and shaft, thereby contracting the bushing to grip the shaft and expanding the hub to grip the discs. By a reverse operation of said means, the bushing can be dewedged or loosened, whereupon the hub 12 by virtue of its resiliency will resume its natural unexpanded state, thus freeing the discs for sliding movement on the hub and allowing adjustment of the sheave body to be made by turning the adjusting screw 15.

Said adjusting screw 15, arranged beside the hub in the surrounding adjustable sheave body, is operatively associated with three adjacent discs of the sheave. The screw extends through and in threaded engagement with the intermediate disc of the trio with which it is associated, the ends of the screw being in abutting relation to the other discs of said trio, so that axial thrust of the screw in either direction is against a disc adjacent to the intermediate one in which the screw is threaded. The screw as a coarse threaded portion 16 threaded in said intermediate disc and a fine threaded portion 17 engaged by a nut 18 held n fixed relation to the hub. As shown, said nut is fitted in a transverse hub slot 19 in which it is held by the screw. Since the coarse thread of the screw is of a p1tch twice that of the fine thread, both threads progressing 1n the same direction, a turn of the screw will cause it to move axially in the nut and to move the disc in which it is threaded an equal distance in the opposite direction. .s the screw moves axially, it moves with it the disc against which it bears. Since the disc in which the screw 18 threaded and the adjacent discs buttedby the screw ends are of different shiftable groups, the discs of each gr up being rigidly connected in appropriate spaced relation, it follows that by rotating the adjusting screw the two groups of discs can be shifted simultaneously equal distances in opposite directions, the total relative movement being twice as great as the axial movement of the screw.

In the illustrated sheave, the ad usting screw 15 .18 associated with the first three discs 1, 2 and 3, being in coarse threaded engagement with 2 and having its ends butting the discs 1 and 3. The screw ends are to be considered. as in butting relation to the discs 1 and 3 even though there may be a slight clearance between either of said discs and the corresponding end of the screw when it bears at its other end against and moves with it the other of said discs 1 and 3. In this instance the fine threaded portion 17 of the screw extends rearwardly, the nut 18 being behind the disc 2. The coarse and fine threaded portions of the screw are shown as of different diameters,

which avoids engagement of both threads by the disc 2. Preferably the fine threaded portion of the screw is of smaller diameter than the coarse threaded portion, permitting use of a nut 18 of smaller size than would otherwise be necessary. The disc 3 has a recess 20 in which the nut 18 is contained when the two shiftable groups of sheave discs are in the relationship shown in Fig. 2. The disc 1 has a recess 21 in which the fore end portion of the adjusting screw is rotatably fitted. The screw has in its fore end .a wrench socket 22 accessible to a wrench through aihole 23 in the disc 1.

Looking at Fig. 2, a turn of a right handed adjusting screw 15 in a clockwise direction as viewed in Fig. 3 will cause it to move axially rearwardly in the nut 18, in which movement the screw bears against and moves with it the disc 3, wherefore the shiftable group of connected discs 1, 3 and 5 moves with the screw rearwardly or to the left in the drawings. At the same time the disc 2 and hence the group of connected discs 2, 4 and 6 moves forwardly or to the right a distance equal to that which the disc 3 moves to the left. By continued clockwise rotation of the screw, the two relatively shiftable groups of discs can be moved to the position shown in Fig. 1. By reverse operation of the adjusting screw, said groups can be returned to the Fig. 2 position.

In assembling the illustrative sheave, the disc 2, adjusting screw 15 and nut 18 are asssembled with the hub 12 in the following manner: While holding the nut 18 in place on the hub, the disc 2 is slipped on the hub and moved to a position against the nut. The screw 15 is then inserted and engaged with the nut as in Fig. 4, before the larger diameter coarse threaded portion of the screw enters the screw-hole in the disc 2. The screw is then screwed up until its coarse threaded portion engages in said disc and moves it a substantial distance from the nut, preferably to the position shown in Fig. 5. The other discs, spacers and tie bolts may then be assembled with the disc 2 in an obvious manner.

The hub 12, in the form shown, is split for its full length by the slot 3%, and is further split from its fore end for the major portion of its length by the slits 31 extending to holes '32 in the hub, as shown in Figs. 10 and 11. The construction shown permits outward flexing of the fore ends of the portions of the hub between the several splits thereof. The hub bore in this instance is tapered inwardly from its rear end to a portion of the bore of uniform diameter (Figs. 1 and 10). The bushing 13 fits the tapered portion of the hub bore and has a cylindrical extension loose or slidably fitting in the bore portion of uniform diameter. The bushing may be keyed to the shaft on which it is to he fitted by a key engaging in the keyway 33 of the bushing. Except for use of the sheave under heavy or sudden shock load conditions, it would not be necessary to key the bushing to the hub; however the bushing may be keyed to the hub by a key 34 fixed in a groove in the bushing and engaging in the hub slot (Figs. 7 and 9). Said key 34 is of such width as to allow the hub to assume its natural unexpanded state without interference. The bushing is split longitudinally as indicated at 35 (Figs. 6 and 7). Fitted in and attached to the fore end of the hub 12 is an annular plate 4t Said plate and hub have abutting beveled surfaces 41, and the plate has a shoulder 42 engagmg behind the internal shoulder 43 in the hub. Sa1d plate can be assembled with the hub, before mount- 111g the sheave discs on the hub, by forcing said plate into place, as is allowable by the expansibility of the hub and flexibility of the portions thereof between the splits thereof. The plate is held from rotation in the hub by a pm 44 projecting from said plate into the hub slot 30 (Fig. 9).

Mounted in the bushing 13 is a cross member 45 having its end portions fitted loosely in diametrically opposite holes therefor in the bushing, said member being insertable into place through one of said holes. Said member and holes are preferably round for easy manufacture. Said member is held from turning in the bushing by a pin 46 projecting from said member into a notch 47 in the bushing (Figs. 1, 3 and 9). The length of said member is such that it cannot move endwise other than slightly, endwise movement thereof being limited by the inside surface of the hub.

The plate 40 and member 45 are connected by a central screw 50 by operation of which the hub and bush- The plate may be referred to as a ring nut. member may be referred to as the bushing movement of the hub and bushing effected the screw will be said screw.

As before indicated, place in the fore end of the ring nut 40 is forced into the hub before the sheave discs The bushing 13 and means connecting it to said ring nut may be assembled in the hub either before or after but preferably after the discs are mounted on the hub. This As the bushing is pushed to the position shown in Fig. 25, the tapered or rounded inner end of the screw shank 51 The wedging screw is now rotated in the direction for screwing it into the bushing nut. As 1, it draws to the position shown in Fig. 1.

In Fig. l, the bushing 13 fits closely in the hub 12 but not so tightly as to contract the bushing or to expand the hub. The bushing may be slip-fitted on the stub extension of a machine shaft (not shown). By screwing up the screw 50, the bushing is drawn tight into the hub, thereby frictionally clutching the hub to the shaft by coaction of the tapered surfaces of the hub and bushing,

mounted thereon. In this operation the fore end of the hub is expanded by coaction of the beveled surfaces 41 of the hub 12 and ring nut 40. Thus the hub is expande both by the bushing and by said ring nut, and hence in its uncontracted state, in the sense that the resistence of the hub to expansion is much less than the resistence of the bushing to contraction. Hence as the bushing is wedged or drawn into the hub by operation of the screw 50, the hub will expand and grip the sheave discs before the bushing contracts. This gives assurance of effective locking of the several sheave hub, as is very desirable for reasons hereinbefore stated.

By a reverse operation of the wedging screw 50, the bushing can be dewedged or loosened sufiiciently to en able the hub to resume its unexpanded state, thus freeing the sheave discs for sliding movement on the hub and allowing adjustment of their positions to be made by operating the adjusting screw 15.

The present invention with respect to the adjusting means may be embodied in various specifically different constructions, some of which are illustrated in Figs. 12, 13 and 16. These figures are longitudinal half sections of dual belt sheaves of similar general construction to that of the sheave first described. It will be understood nut as in Fig.

merals 301, 302,

'disc 302, and v engaged by a nut 318 fixed relative to the hub in front of that in each of said figures the first and third discs are for wedging and dewedging the bushing, and for efi'ecting expansion of the hub by the Wedging action, arethe same as in the sheave first described. In said Figures: l2, l3 and 16 the hub and bushing are designated by the symbols 12 and 13 being similar to those first described but somewhat shorter. The bushing 13 is also shown as tapered for its full length.

In Fig. 12, the sheave discs are designated by the numerals 101, 102, 103 and 104. e adjusting screw 115, identical to 15, is operatively associated with thesecond, third and fourth discs of the series in the same manner in which 15 is associated with the first three discs in Fig. 1. That is to say, the adjusting screw extends through the disc 103 with its ends in butting relation to the discs 102 and 104, the coarse threaded larger diameter portion of the screw being threaded in 103 and its fine threaded rearwardly and engaged by a nut 118 in to the hub behind said disc 103. In this instance the disc 104 has a recess 120 to contain said nut when the discs are in the relationship shown in Fig. 1. The wrench socket in the fore end of the adjusting screw group of connected discs 102 and 104, while causing the group of connected discs 101 and 103 to move an equal distance forwardly. It will be observed that rearward travel of the screw causes adjustment of the sheave to rearward travel of the screw 15 in Figs. 1 and 2 effects adjustment of the sheave to contract the belt grooves.

In Fig. 13, the sheave discs are designated by the numerals 201, 202, 203 and 204. The adjusting screw 215 is operatively associated with the first three discs but in a position reversed to that of 15 in Fig 1. Here the adjusting screw 215 extends through the disc 202 and butts the discs 201 and 203, the coarse threaded larger diameter portion of the screw being in threaded engagement with said disc 202 and the fine threaded smaller diameter portion of the screw extending forwardly and engaged by a nut 218 fixed in relation to the hub in front of said disc 202. In this instance the front disc 20.1 has a recess 220 to contain the nut 218 when the sheave discs are in the relationship shown in Fig. 13. When the screw 215 is rotated to travel forwardly in the nut, it moves the group or plurality of connected discs 20! and group of connected discs 202 and 204 rearwardly. On reverse rotation, the screw moves said groups in the op posite directions. In this instance, rotation of the screw to feed forwardly effects adjustment of the sheave to expand the belt grooves.

slipped on the hub to a position behind and against the 14. The screw 215 is shown in Fig. 14 and engaged with the nut. The screw is then turned in the nut to cause the coarse threaded larger diameter portion of the screw to engage in and to move the disc 202 away from the nut as in Fig. 15. R0- tation of the screw is continued to bring the disc 202, screw and nut to the relationship shown in Fig. 13, Whereupon the other sheave discs, spacers and tie bolts may be assembled with the disc 202.

In Fig. 16 the sheave discs are designated by the nu- 303 and 304. The adjusting screw 315. shown in association with the first three discs, differs from 15 in that the fine thread of 315 is on its larger diameter portion 317, the coarse thread thereof being on its rearwardly extending smaller diameter portion 316. Said screw 315 extends through the disc 302 and butts the 301 and 303, with the smaller diameter coarse threaded portion of the its larger diameter fine threaded portion said disc 302. In this instance the foremost disc 301 has 203 forwardly therewith, while moving the discs screw in threaded engagement with said contain the nut when the a recess 320 to relatively shiftable groups of discs are in the position shown in Fig. 16. The disc 3% has also a recess 324 to receive the rear end portion of the larger diameter portion of the adjusting screw when said groups are in said position. When the screw is operated to travel forwardly in the nut, it moves the group of connected discs 3M and 3d? forwardly therewith, while moving the group of connected discs 3&2 and 304 rearwardly. On reverse operation the screw traveling rearwardly adjusts the sheave to contract the belt grooves.

To assemble the disc 3&2, adjusting screw 315 and nut 318 with the hub, place the nut in position on the hub and insert the screw in position for entry of the larger diameter fine threaded portion 317 into the nut. Turn the screw until said larger diameter portion thereof enters and engages in the nut for about from one-third to onehalf of the thickness of the nut, as in Fig. 17. Then place the disc 302 on the hub in position for entry of the coarse threaded small end of the screw into the screw-hole therefore in said disc, as shown in Fig. 17. Now rotate the screw to cause its smaller diameter coarse threaded portion 316 to engage in said disc and move it toward the nut, as in Fig. 18. Continue to turn the screw until said disc, screw and nut come to the relationship shown in Fig. 16, whereupon the other discs, spacers and tie bolts can be assembled with the disc 3152.

Each of the sheaves shown in the drawings is so designed that by operation of the adjusting screw confronting discs can be moved toward and away from each other between two limits of adjustment. At one of said limits, e. g. when the sheave of Fig. l is fully expanded as in Fig. 2, or when the sheaves of Figs. 12, 13 and 16 are fully contracted as in said figures, the fixed position nut engaging the fine threaded portion of the adjusting screw is fully within the recess therefore in that one of the discs which is butted by the screw end adjacent to the nut. Said nut is of such thickness and so located as to permit opposite movements of the two shiftable groups of discs between the limits of adjustment referred to. The fine threaded portion of the adjusting screw is of a length at least as great as the travel of the screw plus the thickness of said nut, and the coarse threaded portion of said screw is of a length sufficiently greater than the travel of said screw to provide under all conditions ample threaded engagement between said screw and the disc in which it is screwed.

Inasmuch as the adjusting screw in each of the illustrated sheaves is engaged by a non-rotatable nut in fixed position on the hub, said screw being connected with one group of discs for moving it axially with the screw and being connected with the other group of discs by threaded engagement of the screw with one of the discs of said other group, the adjustable sheave body comprised by said groups is at all times held in proper position on the hub. Assuming the coarse thread of the screw to be of a pitch twice as great as that of the fine thread, there is no opportunity for shifting of centers of the belt grooves relative to the hub.

Although the locking of the sheave discs to the hub by expansion of the latter is highly advantageous, the invention with respect to the means for adjusting the position of the sheave discs is not limited to that feature. Obviously any adjusting means in accordance with the invention may be employed in a sheave in which the discs are slidably fitted on a solid or unsplit and inexpansible hub, as for example in the previously mentioned patent.

The sheave shown in Figs. 19 to 22 has the discs thereof slidably fitted on a solid hub 12 which in this instance is a taper-bored hub similar in form to 12 but without the slot and slits 31 of 12. Fixed in the fore end of 12 is a ring nut similar to 4t) but made as a composite article to permit assembly with the solid hub 12 Said composite ring nut 40 is split transversely of its axis into the two pieces and 56 separately connected by the screws 57. The piece 55 provides a shoulder engaging behind an internal shoulder in the hub, said shoulders corresponding to 42 and 43 in Fig. 1. Said composite ring nut 49 is held from rotation relative to the hub by the pin 44 which in this instance engages in the notch 58 in the fore end of the solid hub. In said Figs. 19 to 22, the bushing 13 and elements 45 and 5% connecting it to the ring nut 40 are identical to the correspondingly designated parts of the two-belt sheaves previously described.

In said Figs. 19 to 22, the sheave discs 1 2, 3 and thereby locking the whole series of discs in adjusted position. As in the two-belt sheaves previously described, so also in that of said Figs. 19 and 22 the first and third discs l and 3 are rigidly connected in spaced relation by the spacers 8 and tie bolts and the second and fourth discs 2 and 4 are similarly spaced and connected by the spacers 10 and tie bolts 11. The adjusting means shown in said Figs. 19 to 22, comprising the screw 15 arranged as shown and having its fine threaded extension engaged by the nut 18 held in fixed position on the hub, is identical to the adjusting means of Fig. l.

The sheaves of Figs. 23 and 24 are of substantially identical construction to that of Figs. 19 to 22 except in the following respects.

In Fig. 23, the foremost disc l contains in a threaded hole therefor a locking screw 65 which can be screwed against the head of the adjusting screw 15 to lock it in adjusted position and thereby to lock the sheave discs in adjusted position. The locking screw has a wrench socket in its fore end. When the locking screw is removed, the wrench shank may be passed through the screw-hole into engagement with the wrench socket in the adjusting screw.

In Fig. 24, the adjusting screw 15 is locked by a radially disposed set screw 67 engaging in a central extension of the foremost sheave disc 1 and bearing against the side of the screw head. In this figure, the adjusting screw and clear hole therefore in 1 are extended to locate the screw head in said central extension of 1.

The plural belt sheaves herein described and those disclosed in my copending application Serial No. 277,639 for Adjustable Sheaves, filed March 20, 1952 concurrently herewith, exemplify different species of a common generic invention with respect to the adjusting means. In the species herein illustrated, the adjusting screw is swiveled to one of the axially shiftable groups of discs by abutting of the screw ends against the discs adjacent to opposite sides of the one in which the screw is threaded, whereas in the species illustrated in said copending application the adjusting screw connects only two confronting or adjacent discs solely by threaded engagement with one of them and a direct swivel coupling to the other for moving the latter axially with the screw in either direction. Claims for the generic invention in plural belt sheaves are made in this application, while said copending application contains claims for both single groove and plural belt sheaves embodying the species of adjusting means disclosed therein.

1 claim:

1. A variable pitch V-belt sheave having two interarranged and oppositely axially shiftable groups of annular discs cooperating to form belt grooves, the discs of each group being rigidly connected in spaced relation and arranged in alternation with and confronting those of the other group, a central support carrying said groups of discs in driving connection therewith, a differential screw parallel to the sheave axis extending through and in threaded engagement with a disc of one of said groups and swiveled to the other group for moving the latter axially with the screw, and a non-rotatable nut in fixed position on said support engaging said screw, the interengaging threads of said screw and disc in which it is screwed progressing in the same direction as and being of a pitch greater than that of the interengaging threads of said nut and screw, whereby said groups of discs can be shifted simultaneously in opposite directions by said screw.

2. A sheave according to claim port has in its periphery a transverse groove in nut fits and is held by said screw.

3. A sheave according to claim 1 wherein said support has means engaged by said nut to hold the nut from rotation and from axial movement, the nut being held in engagement with said means by said screw.

4. A sheave according to claim 1 having the disc in which said screw is threaded arranged between said nut and an adjacent disc confronting the one in which the screw is threaded.

5. A sheave according to claim 1 having said nut arranged between adjacent discs one of which is the disc in which the screw is threaded and the other of 1 wherein said supwhich said which has a recess to contain said nut when said adacent discs are in their nearest relation.

6. A sheave according to claim 1 having said nut arranged between adjacent ncn-confronting discs one of which is the disc in which the screw is threaded and the other of which has a recess to contain said nut when said adjacent discs are in their nearest relation.

7. A sheave according to claim 1 having said nut arranged between adjacent confronting discs one of which is the disc in which the screw is threaded and the other of which has a recess to contain said nut when said adjacent discs are in the nearest relation.

8. A sheave according to claim 1 wherein the coarse threaded and fine threaded portions of said screw are of sulficiently different diameters to prevent engagement of the fine thread by said screw by the disc in which said screw is threaded.

9. A sheave according to claim 1 wherein the spacing of the discs of the two groups and the construction and arrangement of the adjusting means are such that by operation of said screw said groups can be simultaneously shifted equal distances in opposite directions between two extreme positions in one of which confronting discs abut and in the other of which non-confronting discs abut.

10. A variable pitch V-belt sheave having two interarranged and oppositely axially shiftable groups of annular discs cooperating to form belt grooves, the discs of each group being rigidly connected in spaced relation and arranged in alternation with and confronting those of the other group, a central support carrying said groups of discs in driving connection therewith, a differential screw parallel to the sheave axis extending through and in threaded engagement with an intermediate disc of the series comprised by said groups, the ends of which screw butt the adjacent discs at opposite sides of said intermediate disc, and a non-rotatable nut in fixed position on said support engaging said screw between said intermediate disc and one of the discs adjacent thereto, the interengaging threads of said screw and intermediate disc progressing in the same direction as and being of a pitch greater than that of the interengaging threads of said nut and screw, whereby said groups of discs can be shifted simultaneously in opposite directions by said screw.

11. A sheave according to claim 10 wherein that one of the discs which is butted by the screw end adjacent to said nut has a recess to receive said nut as said one of the discs and said intermediate disc are moved toward each other.

12. A sheave according to claim 10 wherein said screw has a wrench socket in an end thereof and the disc which said end of the screw butts is an end disc having a hole through which a wrench shank can be inserted for engaging in said socket.

13. A sheave according to claim 10 wherein said screw has a wrench socket in an end thereof and the disc which said end of the screw butts is next to an end disc, said end disc and disc next thereto having registering passages through which a wrench shank can be inserted for engaging in said socket.

14. A sheave according to claim 10 wherein the fine threaded portion of said screw extends rearwardly from the coarse threaded portion thereof, said nut being between said intermediate disc and the one behind it.

15. A sheave according to claim 10 wherein the fine threaded portion of the screw extends forwardly from the coarse threaded portion thereof, said nut being between said intermediate disc and the one in front of it.

16. A sheave according to claim 10 wherein the coarse threaded portion of said screw is of a diameter sufiiciently larger than that of the fine threaded portion to avoid engagement of the latter by said intermediate disc when relatively close to the disc butted by the small diameter end of the screw, said nut being between said intermediate disc and the disc butted by the small diameter end of the screw, said last mentioned disc having a recess to receive said nut as said disc and said intermediate disc are moved toward each other.

17. A sheave according to claim 10 wherein the fine threaded portion of the screw is of larger diameter than the coarse threaded portion screwed in said intermediate disc, said nut being between said intermediate disc and that one of the discs butted by the larger diameter end of the screw, said one of the discs having a recess to receive said nut as said one and said intermediate til) 10 disc move toward each other, and said-intermediate dis'c having a recess to receive the inner end of the larger diameter portion of the screw when said one and'mtermediate disc are in close relation,

18. A variable pitch V-belt sheave having two nterarranged and oppositely axially shiftable groups of annular discs cooperating to form belt grooves, the discs of each group being rigidly connected in spaced relation and arranged in alternation with and confronting those of the other group, a central support carrying said groups of discs in driving connection therewith, a diiferential screw parallel to the sheave 'axis operatively associated with the first, second and third discs of the series comprised by said groups, said screw extending through the second disc and butting the first and third discs, sald screw having a coarse threaded portion in threaded engagement with said second disc and a rearwardly extending fine threaded portion of sufficiently reduced diameter to avoid engagement by said second disc, and a non-rotatable nut in fixed position on said support engaging said fine threaded portion between said second and third discs, the coarse and fine threads of the screw progressing in the same direction, whereby said groups of discs can be shifted simultaneously in opposite d1- rections by said screw.

19. A variable pitch V-belt sheave having two interarranged and oppositely axially shiftable groups of annular discs cooperating to form belt grooves, the discs of each group being rigidly connected in spaced relation and arranged in alternation with and confronting those of the other group, a central support carrying said groups of discs in driving connection therewith, a differential screw parallel to the sheave axis operatively associated with the first, second and third discs of the series comprised by said groups, said screw extending through the second disc and butting the first and third discs, said screw having a coarse threaded portion in threaded engagement with said second disc and a forwardly extending fine threaded portion, said coarse threaded portion and screw-hole therefor in the second disc being of sufiiciently larger diameter than said fine threaded portion to prevent engageemnt of the latter by said second disc, and a non-rotatable nut in fixed position on said support engaging said fine threaded portion between the first and second discs, the first disc having a recess to accommodate said nut, the coarse and fine threads of the screw progressing in the same direction, whereby said groups of discs can be shifted simultaneously in opposite directions by said screw.

20. A variable pitch V-belt sheave having two interarranged and oppositely axially shiftable groups of annular discs cooperating to form belt grooves, the discs of each group being rigidly connected in spaced relation and arranged in alternation with and confronting those of the other group, a central support carrying said groups of discs in driving connection therewith, a differential screw parallel to the sheave axis operatively associated with the first, second and third discs of the series comprised by said groups, said screw extending through the second disc and butting the first and third discs, said screw having a coarse threaded portion in threaded engagement with said second disc and a forwardly extending fine threaded portion of greater diameter than that of said coarse threaded portion, and a non-rotatable nut in fixed position on said support engaging said fine threaded portion between the first and second discs, the first disc having a recess to accommodate said nut, the coarse and fine threads of said screw progressing in the same direction, whereby said groups of discs can be shifted simultaneously in opposite directions by said screw.

21. A variable pitch V-belt sheave having two interarranged and oppositely axially shiftable groups of annular discs cooperating to form belt grooves, the discs of each group being rigidly connected in spaced relation and arranged in alternation with and confronting those of the other group, a central support carrying said groups of discs in driving connection therewith, a differential screw parallel to the sheave axis extending through and in threaded engagement with an intermediate disc of the series comprised by said groups, the ends of which screw butt the adjacent discs at opposite sides of said intermediate disc, and a non-rotatable nut in fixed position on said support engaging said screw between said intermediate disc and one of the discs adjacent thereto, said one oi the discshaving a recess to contain said nut when said one and said intermediate disc are in their nearest relation, the interengaging threads of said screw and intermediate disc progressing in the same direction as and being of a pitch twice as great as that of the interengaging threads of said nut and screw, the spacing of the discs of the two groups and the arrangement and proportions of said screw and nut being such that by operation of the screw said groups can be simultaneously shifted equal distances in opposite directions between two extreme positions in one of which confronting discs abut and in the other of which non-confronting discs abut.

References Cited in the file of this patent Number Number UNITED STATES PATENTS Name Date Williams Mar. 13, 1951 Williams Sept. 16, 1952 FOREIGN PATENTS Country Date Great Britain of 1911 

